Filter system and particulate filter unit therefor

ABSTRACT

The invention provides a filter system and particulate filter unit therefor. The filter system may act as a purifier and a muffler for heavy and light duty diesel vehicles. The invention includes one or more combination filter units that remove particulates and nitrogen oxides in successive passes before the gas exits. A particulate filter unit may be used that removes additional particulates.

[0001] This application is a continuation-in-part application of U.S.Ser. No. 09/631,794, filed Aug. 3, 2000, and currently pending.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field

[0003] The present invention relates generally to exhaust filtering and,in particular, to a filter system, regeneration system for the filtersystem, a combined soot removing system and applications of thosesystems. In addition, this invention relates to a particulate filterunit usable with one or more second stage particulate and nitrogen oxidefilter units.

[0004] 2. Related Art

[0005] Filtering of exhaust is a well-known mechanism to reducepollution. Related art devices have suffered from a number of drawbacks.For instance, most of the filters are adaptations of substrates used forautomotive catalytic converters in which alternating channels areplugged to force the gas through the substrate walls. A number of otherfilter configurations and materials have been tried, but none have beenrobust enough or cost effective enough for widespread use. Also, oncethe particulates or other materials have been collected, they must beremoved before the filter can function effectively. This is typicallyaccomplished by igniting and burning the collected burnable particulatesusing a variety of techniques. Current techniques in the art ofregeneration are expensive, complex, and many are outright hazardous,e.g., some use explosive, compressed gas or highly flammable (comparedto diesel fuel) liquids.

[0006] In addition, the catalytic converter materials were designed tooperate at much lower temperatures than can be reached during anuncontrolled regeneration (rapid, uncontrolled burning of the sootcollected in the filter). In many cases, the filter media cracks, melts,or is otherwise damaged by either vehicle induced vibration or very hightemperatures. In addition, many filters include two or more integralfilter sections for filtering different pollutants. Unfortunately, thesefilters make regeneration difficult. Further, when one filter section isin need of repair, all of the sections must be replaced.

[0007] Another problem with related art devices is their inability toaccommodate different applications because of their inflexible size. Anew mold must be made for each different size filter unit, whichdramatically increases cost or limits the ability to tailor the filterfor the application. U.S. Pat. No. 5,250,094 to Chung et al. discloses afilter construction having a number filter sections 114. Unfortunately,the device is limited in application by the size of the enclosure.

[0008] Related art devices also do not adequately provide a regenerationsystem that is safe and controllable. In particular, U.S. Pat. No.5,820,833 to Kawamura includes an electric wire net that is integralwith a filter, i.e. in-filter regeneration. Since the regenerationsystem and filter are inseparable, the device may be subject tovibrations that may induce damage. U.S. Pat. No. 5,394,692 toTeuber-Ernst discloses a separate regeneration system that is fired byan explosive gas, which is an unsafe situation when in an environmentwhere other fuel sources are nearby. Another problem with theseregeneration systems is their inability to adequately control the rateof burn and, therefore, the temperature of the filter duringregeneration. Many filters cannot withstand the repeated exposure tohigher temperatures caused by some regeneration systems. Further, thepotential for regeneration to proceed uncontrollably is potentiallydangerous due to the extreme amount of heat that is generated by theburning soot.

[0009] Accordingly, there is a need in the art for a filter thatincludes separate filtering sections for ease of repair andregeneration. Furthermore, there is a need for a readily size-adjustablefilter system. It would also be advantageous if this filter could beretrofitted to a variety of exhaust producing devices that exhaust avariety of different pollutants. Moreover, there is also a need for asafe and controllable regeneration system. A system that combines theabove filter and regeneration system would also be advantageous.

[0010] In addition, a system with improved particulate removal would beadvantageous.

SUMMARY OF THE INVENTION

[0011] The invention provides an exhaust filter system that serves as aparticulate trap, a muffler, and a purifier. The filter system designremoves the structural load from the filter. The invention provides forlonger filter life, less complicated regeneration, less modification toan exhaust producing device for retrofitting, and much lower life cyclecosts to the end user. In addition, the filter system can tolerate muchhigher temperatures than conventional filter systems thereby increasingthe durability and use range of the filters. The invention also providesa particulate filter unit to remove additional particulates.

[0012] In a first aspect of the invention is provided a filter unit foran exhaust removing filter system having one or more attachable unitsfor varying the size of the filter system, the filter unit comprising: ahousing; a plurality of concentrically arranged particulate filterswithin the housing; a plurality of first passages passing adjacent atleast one particulate filter and opened to a first end of the housing;and a plurality of second passages passing adjacent at least oneparticulate filter and opened to a second end of the housing. Exhaustpasses through one of the particulate filters as the exhaust moves fromthe first passages to the second passages.

[0013] A second aspect of the invention includes a filter system forremoving soot from exhaust of an exhaust producing device, the filtersystem comprising one or more attachable units for varying the size ofthe filter system, the system comprising: a particulate filter unit; andone or more combination particulate and nitrogen oxide filter units.

[0014] A third aspect of the invention provides a filter system forremoving soot from exhaust of an exhaust producing device, the filtersystem comprising one or more attachable units for varying the size ofthe filter system, the system comprising: a first stage unit housing; aplurality of concentrically arranged particulate filters within thefirst stage unit housing; a plurality of first passages passing adjacentat least one particulate filter and opened to a first end of the firstunit stage housing; a plurality of second passages passing adjacent atleast one particulate filter and opened to a second end of the firstunit stage housing; whereby exhaust passes through a particulate filteras the exhaust moves from the first passages to the second passages; andone or more second stage units, each second stage unit including: asecond stage unit housing; a particulate filter section positionedwithin the second stage unit housing; and a nitrogen oxide filtersection having a gas-impervious inner cylinder spaced within theparticulate filter section and a nitrogen-oxide removing catalystpositioned within the inner cylinder.

[0015] A fourth aspect of the invention includes a filter unit for anexhaust removing filter system having one or more attachable units forvarying the size of the filter system, the filter unit comprising: ahousing; a plurality of concentrically arranged particulate filterswithin the housing; a set of intake openings in a first end of thehousing, each intake opening communicating with a passage extendingadjacent an intake side of at least one particulate filter; a set ofoutput openings in a second end of the housing, each output openingcommunicating with a passage extending adjacent an output side of atleast one particulate filter; and wherein exhaust enters the intakeopenings, passes through a respective particulate filter and exitsthrough the output openings.

[0016] A fifth aspect of the invention is directed to a filter systemfor removing soot from exhaust of an exhaust producing device, thefilter system comprising one or more attachable units for varying thesize of the filter system, each unit including: means for housing filtercomponents; means for filtering particulates positioned within the meansfor housing; and means for filtering particulates and nitrogen oxide.

[0017] A sixth aspect of the invention is directed to a filter systemfor removing soot from exhaust of an exhaust producing device, thefilter system comprising one or more attachable units for varying thesize of the filter system, the system comprising: a particulate filterunit including a particulate filter unit housing; a plurality ofconcentrically arranged particulate filters within the particulatefilter unit housing; a plurality of first passages passing adjacent atleast one particulate filter and opened to a first end of the first unitstage housing; a plurality of second passages passing adjacent at leastone particulate filter and opened to a second end of the first unitstage housing; whereby exhaust passes through a particulate filter asthe exhaust moves from the first passages to the second passages; andone or more combination filter units each including: a combinationfilter unit housing having an outer shell and a coupling adapted toattach a unit to an adjacent unit; a particulate filter sectionpositioned within the combination filter unit housing; a porous cylinderfor supporting an inner portion of the particulate filter section; agas-impervious inner cylinder spaced within the porous cylinder; and anitrogen-oxide removing catalyst positioned within the inner cylinder,wherein exhaust gases pass radially through the particulate filtersection and longitudinally through the nitrogen oxide filter.

[0018] The foregoing and other features and advantages of the inventionwill be apparent from the following more particular description ofpreferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The preferred embodiments of this invention will be described indetail, with reference to the following figures, wherein likedesignations denote like elements, and wherein:

[0020]FIG. 1 is a cross-sectional view of a filter system in accordancewith the invention;

[0021]FIG. 2 is an exploded view of a unit of the filter system;

[0022]FIG. 3 is a cross-sectional view of a unit of the filter system;

[0023]FIG. 4 is a detailed cross-sectional view of a three unit filtersystem;

[0024]FIG. 5 is a cross-sectional view of an alternative aspects of aunit of the filter system;

[0025]FIG. 6 is a side view of a soot removing system including aregeneration system in accordance with the invention;

[0026]FIG. 7 is a motor vehicle incorporating the systems of theinvention;

[0027]FIG. 8 is a cross-sectional view of a filter system in accordancewith a second embodiment of the invention;

[0028]FIG. 9 is perspective view of a particulate filter used in thefilter system of FIG. 8; and

[0029]FIG. 10 is a cross-sectional view of the particulate filter ofFIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Although certain preferred embodiments of the present inventionwill be shown and described in detail, it should be understood thatvarious changes and modifications may be made without departing from thescope of the appended claims. The scope of the present invention will inno way be limited to the number of constituting components, thematerials thereof, the shapes thereof, the relative arrangement thereof,etc., which are disclosed simply as an example of the preferredembodiment.

[0031] For convenience, the disclosure will be broken down into thefollowing headings for organizational purposes only:

[0032] I. Filter System

[0033] II. Regeneration System

[0034] III. Combined Soot Removing System

[0035] IV. Applications

[0036] V. Particulate Filter Unit

[0037] I. Filter System:

[0038] Referring to the FIGS. 1-5, a filter system 10 for removing sootfrom the exhaust of an exhaust producing device 12 is shown. Filtersystem 10 includes one or more attachable units 14 for varying the sizeof filter system 10 that are preferably cylindrical in cross-section. Asshown, a number of units 14A, 14B, 14C, etc. may be sealingly coupledtogether to create a filter. In this case, a shell support 18 may beprovided to secure a lower unit 20. Alternatively, as shown in FIG. 4, anumber of units 14 can be stacked into a shell 16 to produce filters ofvarious capacities. Shell 16 may be a standard muffler shell of, forinstance, a diesel engine driven truck. Shell 16 is preferably made ofstandard muffler steel.

[0039] As shown best in FIGS. 1-3, each unit 14, 14A, 14B, etc. includesa housing 22, a particulate filter section 24 and a nitrogen oxide (NOX)filter section 26. Housing 22 encloses filter sections 24, 26 and ispreferably made of a corrosion-resistant metal such as high temperature,stainless steel like AISI types 301-325 or 401-440. Each housing 22 alsoincludes a coupling 23 for sequentially attaching a unit 14A to anadjacent unit 14B. Coupling 23 may take a variety of forms known tothose skilled in the art; as shown, coupling 23 includes an interferencefit-type coupling such that each unit 14 has a recessed portion thatfits into an expanded portion of an adjacent unit 14. This providesstructural rigidity and support for the stack. Other mechanisms ofattachment such as clips may also be provided.

[0040] Particulate filter section 24 includes a filtering section 28having either a set of radially oriented plates or a set of radiallyoriented pleats 30, and a porous cylinder 32 for supporting an innersurface of plates or pleats 30. Plates or pleats 30 are composed of lowback pressure filter media such as woven ceramic fiber, ceramic fibercloth, ceramic fiber paper/felt or a combination of those materials. Thefibers are preferably one of the following ceramic materials: aluminumoxide, silicon dioxide, mullite (a mixture of aluminum oxide and silicondioxide), aluminosilicate (another mixture of aluminum oxide and silicondioxide), silicon carbide, silicon carbonitride, or silicon oxycarbide.Ceramic fiber plates or pleats 30 are preferably rigidized, protected,and rendered more durable by a thin coating of ceramic. This media isfurther improved and stiffened by the use of a coating of pre-ceramicpolymers such as that disclosed in U.S. Pat. No. 5,153,295 to Whitmarshet al., hereby incorporated by reference. Preferably, the pre-ceramicpolymer is selected from the group comprising: silicon carbide,oxycarbide, aluminosilicate and alumina. It should be recognized thatother pre-ceramic polymers may also be possible. The ceramic coating andpre-ceramic polymers are fired to form a ceramic coating on plates orpleats 30. Filtering section 28 is then more resistant to damage thantypical materials used for filters because the ceramic protects thefibers from the exhaust gas, prevents the fibers from rubbing againsteach other, and prevents plates or pleats 30 from flexing sufficientlyto damage each other. An outer surface 31 of plates or pleats 30 has asmaller outer diameter than an inner diameter of housing 22 to create asubstantially annular chamber 33 for passage of exhaust therebetween.Couplings 23 are also separated from outer surface 31 of plates orpleats 30 to provide for the continuation of annular chamber 33 betweenunits 14.

[0041] Porous cylinder 32 is preferably constructed of acorrosion-resistant metal such as high temperature, stainless steel likeAISI types 301-325 or 401-440.

[0042] Nitrogen oxide filter section 26 includes a gas-impervious innercylinder 34 and a nitrogen-oxide removing catalyst 36 positioned withininner cylinder 34. Inner cylinder 34 is spaced from an inner portion ofparticulate filter section 24 to create a substantially annular chamber38 therebetween, i.e., cylinder 34 has a smaller diameter than an innerdiameter of porous cylinder 32. Inner cylinder 34 is preferablyconstructed of a corrosion-resistant metal such as high temperature,stainless steel like AISI types 301-325 or 401-440, and has open ends35. NOX catalyst 36 is preferably composed of a non-porous ceramicmaterial that is bonded into gas-impervious cylinder 34. Examples ofmaterial suitable for catalyst 36 are: codierite, mullite, siliconcarbide and aluminum oxide. It should be recognized, however, that othertypes of ceramic catalyst support media may be used and any nitrogenoxide catalyst material available commercially may be suited for usewith the invention.

[0043] Each unit 14 also preferably includes a first, upper end cap 40and a second, lower end cap 42. End caps 40, 42 function to seal off theends of plates or pleats 30 and annular chamber 38. Additionally, eachend cap 40, 42 includes a central aperture 46 that acts to positionnitrogen oxide filter section 26 and, in particular, inner cylinder 34,such that section 26 is substantially concentric within particularfilter section 24.

[0044] A special end cap 44, referred to as a stop cap, may be providedon a lowermost unit 14, as shown in FIGS. 1, 4 and 5. Stop cap 44 doesnot include a central aperture 46 and may be formed as a solid member ormay include a plug 48, shown in FIG. 4, to close aperture 46. Asillustrated in FIG. 5, stop cap 44 may also include an exhaust directingformation 50 for directing exhaust into nitrogen oxide filter section26. Formation 50 may be created by, for example, stamping a solid stopcap 44 or plug 48. Another stop cap 45, shown in FIG. 1, may be providedto seal an uppermost unit 14 of filter system 10. Stop cap 45 preferablyseals to housing 22 of the uppermost unit 14, as shown in FIG. 1, toprevent exhaust 52 from escaping through annular chamber 33. Sealing isprovided by the use of compressible fiber gasketing, rigidized fiberfelt or a polymer slurry. Alternatively, as shown in FIG. 5, a filtersystem output shroud 47 may be coupled directly to housing 22 toeliminate the need for stop cap 45. A vent port 49 may also be providedon gas impervious cylinder 34 to mate with an adjacent unit 14 and,hence, direct exhaust 52 from one NOX filter section 26 to the next(shown in FIG. 1), or to direct exhaust 52 through shroud 47 (shown inFIG. 5).

[0045] Each end cap 40, 42, 44, 45 and plug 48 are preferably made of acorrosion-resistant metal such as high temperature, stainless steel likeAISI types 301-325 or 401-440. Filtering section 28 may be sealed to theappropriate caps 40, 42, 44, 45 by the use of compressible fibergasketing, rigidized fiber felt or a polymer slurry.

[0046] Operation of filter system 10 will be described with reference toFIGS. 1, 4 and 5. In operation, exhaust 52 from an exhaust producingdevice 12 is directed to filter system 10 by an adaptor 54. Adaptor 54is preferably made of standard muffler steel. Adaptor 54 is preferablyin the form of an inverted Y with three openings 56, 58 and 62. Firstopening 56 is shaped and sized to mate with a lowermost unit 14 offilter system 10; second opening 58 is shaped and sized to mate with anexhaust port 60 of exhaust producing device 12; and third opening 62 isshaped and sized to mate with a regeneration system 64, as will bedescribed below. As will be recognized by those skilled in the art,adapter 54 may also require other adapter components (not shown) forproper coupling to filter system 10, exhaust producing device 12 andregeneration system 64.

[0047] Referring to FIG. 1, during operation of filter system 10, thirdopening 62 is closed by a flange or valve 66. Exhaust 52 from exhaustproducing device 12 is communicated by adapter 54 to filter system 10where it enters annular chamber 33 between housing 22 and particulatefilter section 24. Exhaust 52 may pass from one unit 14B to an adjacentunit 14A within annular chamber 33, and so on through all of the unitsin system 10. As exhaust 52 is routed through chamber 33, it radiallyenters particulate filter section 28, i.e., it moves inwardly, whereparticulates from the exhaust 52, such as soot, sulfates, oxides andother particulates are removed. Subsequently, exhaust 52 is routedthrough porous cylinder 32 and into annular chamber 38. Because of thesealed ends of annular chamber 38, exhaust 52 is routed into NOX filtersection 26 at an open end 35 of gas impervious cylinder 34 where itpasses longitudinally through section 26. NOX catalyst 36 reacts withand removes nitrogen oxides (NOX) from exhaust 52. Further removal ofNOX is provided as exhaust 52 passes from unit, e.g., 14B, to anotherunit, e.g., 14A and so on through all units 14, i.e., exhaust 52 thatpasses through lower units 14 is subject to repeated NOX removal as itpasses through adjacent unit(s) 14. The resulting exhaust gas, when itemerges from filter system 10 will be significantly depleted in NOX andparticulates. Another advantage of filter system 10 is that it also actsto muffle noise from exhaust producing device 12, i.e., system 10 actsas a muffler and a filter.

[0048] It should be recognized that any number of units 14, 14A, 14B,etc. may be stacked together to form a filter. The particularillustrations of two units (FIG. 1), three units (FIG. 4) and one unit(FIG. 5) are for illustration purposes only. Furthermore, as shown inFIG. 1, NOX filter section 26 may be shorter than particulate filtersection 24 to promote routing of exhaust 52. However, this is notnecessary, as shown in FIG. 5, where stop cap 45 includes formation 50to promote routing of exhaust 52 to nitrogen oxide filtering section 26.

[0049] II. Regeneration System:

[0050] Referring to FIG. 6, a regeneration system 64 of the invention isshown in greater detail. Regeneration entails the burning out of sootfrom a filter, such as filter system 10, to restore the filtrationcapacity of a filter. Regeneration system 64 includes an electricallypowered regenerator or heat source 70 for producing heated gas 72 to bepassed through a filter such as filter system 10 to regenerate thefilter. Regenerator 70 preferably includes an electric powered metalwire, an electric powered ceramic element or an electric poweredintermetallic element having a power rating of 1000-15,000 watts.

[0051] Regeneration system 64 also preferably includes: adaptor 54; anair pump or blower 74 for pressurizing heated gas 72; a source of inertgas 76; and a computer control system 78. Adapter 54, as describedabove, may include a second flange or valve 67 for closing off secondopening 58 to exhaust producing device 12 during regeneration. As analternative, adaptor 54 may simply be disconnected from exhaustproducing device 12.

[0052] Source of inert gas 76 is preferably provided to supply inert gas80 with heated gas 72 to control the burn rate of soot within filtersystem 10, i.e., the amount of inert gas 76 controls the temperature ofthe filter by controlling the amount of oxygen available for burning. Apreferred inert gas for use in system 64 is nitrogen.

[0053] Computer-control system 78 operates to control the regenerationprocess by controlling: regenerator or heat source 70, the temperatureof filter system 10 and air pump or blower 74. In order to control theabove parameters, computer control system 78 may include: a thermocouple84 for measuring temperature in filter system 10 during regeneration; aheat source temperature controller 90; and an air supply controller 92.Thermocouple(s) 84 may be provided anywhere along filter system 10 toaccurately determine temperature of filter system 10, e.g., within eachunit 14. Heat source temperature controller 90 controls the amount ofheat produced by regenerator 70, and air supply controller 92 controlsthe amount of air supplied by air pump or blower 74. Advantageously, airsupply controller 92 also may control the amount of inert gas 80supplied from source of inert gas 76.

[0054] Regeneration system 64 also may include a scrubber 82 thatattaches to an outlet of filter system 10. Scrubber 82 collectspollutants generated during the regeneration process.

[0055] In operation, filter system 10 is regenerated once it collectsenough soot to increase the back-pressure therein to a pre-determinedpoint; a condition that may be determined by a pressure gauge (notshown) on filter system 10. At that stage, filter system 10 would bebrought to a regeneration system 64, or vice versa, where regenerator 70is quickly attached to filter system 10 at adaptor 54 opening 62, e.g.,by using flange or valve 66. Second flange or valve 67 is closed toblock flow of heated gas 72 and inert gas 80 to exhaust producing device12. The temperature inside filter system 10 is tracked bythermocouple(s) 84 that feed back information to computer control system78 for control of regenerator 70 and air supply controller 74.

[0056] As heat is applied to filter system 10 from regenerator 70, thesoot will combine with the pumped-in heated gas 72 to burn and generateits own heat. The burning will propagate through filter system 10 andfrom unit 14 to unit 14 until all of the burnable soot is removed. Theeffluent from the burning soot may be cleaned by scrubber 86, if one isprovided, and subsequently vented to the atmosphere. Thermocouple(s) 84may be provided in each unit 14 to monitor temperature. Computer controlsystem 78 may then prevent overheating by decreasing either the heat orthe air supply or increasing the amount of inert gas to maintain acontrolled burn rate.

[0057] After the regeneration process is complete, scrubber 86 andregenerator 70 are disconnected, flange/valve 66 closed, andflange/valve 67 opened for communication with exhaust producing device12. Filter system 10 may then be re-used.

[0058] III. Combined Soot Removing System:

[0059] As also shown in FIG. 6, the invention also includes a sootremoving system 98 that, in general terms, is a combination of aspectsof filter system 10 and regeneration system 64. Soot removing systemincludes a filter, such as filter system 10, for removing soot fromexhaust 52 of an exhaust producing device 12 and a regeneration system64 having an electrically heated regenerator 70 for producing heated gas72 to be passed through the filter to regenerate the filter. Aspect ofthe above-described systems that may be part of soot removing systeminclude: source of inert gas 76 for supplying an inert gas 80, e.g.,nitrogen, to the filter with hot gases 72; adaptor 54 for coupling tothe filter for directing exhaust of exhaust producing device 12 orheated gas 72 from regenerator 70 through the filter. As discussedabove, adaptor 54 preferably includes a first opening 56 coupled to afirst end of the filter, a second opening 58 for coupling to an exhaustport 60 of exhaust producing device 12, a third opening 62 for couplingto regenerator 70; and a valve 66 for closing off second opening 58during regeneration. A scrubber 82 may be attached to an output end ofthe filter.

[0060] In a preferred embodiment, shown in FIG. 6, regenerator 70 isseparate from exhaust producing device 12 and filter system 10.Alternatively, regenerator 70 may be attached to exhaust producingdevice 12, as shown in FIG. 7. Filter system 10 includes one or moreunits 14 including: a housing 22; a particulate filter section 24; and anitrogen oxide filter section 26 having a gas-impervious inner cylinder34 having a first and second open end 35 and a nitrogen-oxide removingcatalyst 36 located within inner cylinder 34. Regenerator 70 includes aheat source chosen from the group comprising: an electric powered metalwire, an electric powered ceramic element and an electric poweredintermetallic element. Regeneration system 64 includes an air pump orblower for pressurizing heated gas 72 and a computer-control system 78.Computer-control system 78 includes: a thermocouple 84 for measuringtemperature in the filter during regeneration, a heat source temperaturecontroller 90; and an air supply controller 92.

[0061] IV. Applications:

[0062] Filter system 10, regeneration system 64 and soot removing system98 in accordance with the invention have applications with a variety ofexhaust producing devices 12. For instance, exhaust producing device 12may be: an engine, a paint booth, a furnace, a stove, a cement makingkiln, an asphalt paving machine, etc. The types of engine the systems10, 64, 98 may be applied to are limitless and include, for example,light and heavy duty diesel engines, one and two cylinder engines, twoand four cycle engines, etc.

[0063] As shown in FIG. 7, another aspect of the invention is theapplication of the above systems to a motor vehicle 100 and, especially,a diesel powered motor vehicle. Motor vehicle 100 includes an engine 104(i.e., an exhaust producing device) for driving ground engaging members106, e.g., wheels or tracks; an exhaust filter 10 for removing soot fromexhaust of engine 104, the filter including one or more attachable units14 for varying the size of the filter; and an electrically heatedregenerator 170 for producing heated gas to be passed through the filterto regenerate the filter. As illustrated, regeneration system 64 can bea part of motor vehicle 100. As an alternative, as illustrated in FIG.6, regeneration system 64 may be a separate system to which a motorvehicle 100 is occasionally attached to, when necessary, forregenerating filter system 10.

[0064] When filter system 10 is used on a motor vehicle 100, units 14may be housed in a metal shell 16, shown in FIG. 6, that isapproximately the dimensions of a muffler, e.g., a diesel muffler, orcan form the muffler themselves. For a typical heavy duty diesel truck,a stack of 3-4 segments would be mounted into a steel muffler shell 16that would be mounted in place of a contemporary muffler. Alternatively,as shown in FIG. 7, units 14 may form the outermost shell of afilter/muffler themselves.

[0065] While a particular application of the invention has beendiscussed, it should be recognized that other applications are possible.For instance, the teachings of the invention may be applied to: heavyduty and light duty diesel engines such as used on trucks or trains;stationary diesel generators, mining vehicles, and power plants; smokeremoval; and the collection and burning/oxidizing (rendering harmless)of Volatile Organic Compounds (VOCs) generated from for paint booths.Additional applications include smoke and hydrocarbon removal forcooking establishments; particulate removal for cement manufacturers;VOC and hydrocarbon emission prevention for asphalt paving equipment;etc.

[0066] V. Particulate Filter Unit:

[0067] Referring to FIGS. 8-10, a particulate filter unit 210 is shownin use with the above-described systems. Filter unit 210 includes ahousing; a plurality of concentrically arranged particulate filterswithin the housing; a plurality of first passages passing adjacent atleast one particulate filter and opened only to a first end of thehousing; and a plurality of second passages passing adjacent at leastone particulate filter and opened only to a second end of the housing.Exhaust passes through one of the particulate filters as the exhaustmoves from the first passages to the second passages.

[0068] As shown in FIG. 8, particulate filter unit 210 may couplebetween adaptor 54 and a lowermost unit 14C of the one or more units 14,described above. Units 14 will hereafter be referred to as “combinationfilter units” or “second stage units” for clarity. Combination filterunits 14 are substantially identical to those described above. As willbe described, particulate filter unit 210 is preferably used as a firststage unit to one or more subsequent second stage combination filterunits 14. However, filter unit 210 may also be positioned anywhere in asequence of units 14 including being the last unit in the sequence. Iffilter unit 210 is positioned in the middle of a sequence, a plenum orspace (not shown) may be provided at the end of unit 210 to directexhaust from central aperture 46 or vent port 49 (FIG. 1) of animmediately preceding combination filter unit 14. Similarly, a stop cap44 may be provided on a subsequent unit 14 to direct exhaust toparticulate filter section 24 properly.

[0069] Turning to FIGS. 9 and 10, filter unit 210 includes a housing 212for enclosing a plurality of particulate filters 214A-D. Housing 212 ispreferably formed of a metal and includes an outer, gas-impervious shell216 and an inner, gas-impervious shell 218. Housing 212 also includes afirst end 224 and a second end 226 that are substantially closed orcapped, as will be described further. A coupling 227 (FIG. 10) forsequentially attaching filter unit 210 to an adjacent combination filterunit, e.g., unit 14C of FIG. 8, is also provided. A coupling 229 may bealso be provided for coupling to adaptor 54 or a preceding combinationfilter unit 14.

[0070] Each particulate filter 214A-D preferably includes an outerporous shell 232, a pleated or plated filter section 234 within outerporous shell 232, and an inner porous shell 236 within filter section234. However, filter sections 234 may be sufficiently rigid so as to notrequire porous shells 232, 234. Filter sections 234 are constructed ofsubstantially the same material as particulate filter section 24, i.e.,ceramic fiber paper, ceramic cloth and ceramic woven fiber coated with apre-ceramic polymer chosen from the group comprising: silicon carbide,oxycarbide, aluminosilicate and alumina.

[0071] Particulate filters 214 are concentrically arranged withinhousing 212 such that a number of passages 220, 222 pass adjacent atleast one particulate filter 214. A passage 220A is also formed betweenan innermost particulate filter 214A and inner shell 218, i.e., innershell 218 is concentrically positioned within innermost particulatefilter 214A. Likewise, a passage 222C is formed between an outermostparticulate filter, e.g., filter 214D in FIG. 10, and outer shell 216.Particulate filters 214 abut, or are otherwise sealed against,respective first and second ends 224, 226 of housing 212 so that gascannot pass about the ends of the filters.

[0072] First and second end 224, 226 of housing 212 include a number ofopenings 228, 230 that determine the passages that receive exhaust to becleaned and those which exit cleaned exhaust. While openings 228, 230are illustrated as being formed by apertures formed in a cap or endpieceof housing 212, it should be understood that openings 228, 230 may beformed in a variety of fashions. For instance, openings 228, 230 may beformed by coupling washer-shape plates to ends of adjacent particulatefilters 214.

[0073] Since the number of particulate filters 214 and passages 220, 222may vary (depending on factors such as the amount of particulate matterpresent in the exhaust, position of filter unit 210, etc.), the numberof openings 228, 230 may vary. For instance, FIG. 9 shows three filters214A-C with two intake and two output openings, and FIG. 10 shows fourfilters 214A-D having three intake openings and two output openings, orvice versa, two intake openings and three output openings. Hence, thenumber of intake openings 228 and output openings 230 may vary toaccommodate different numbers of filters 214 and/or passages 220, 222.

[0074] The positioning of intake and output openings 228, 230 are suchthat an intake opening 228 provides exhaust to be cleaned to an intakeside of at least one particulate filter and an output opening 230 exitsthe cleaned exhaust from an opposite, output side of at least oneparticulate filter. For instance, as illustrated, first end 224 ofhousing 212 includes a number of intake openings 228 that communicateoncoming exhaust 52 (from adaptor 54 or another combination filter unit14) to a first set of the passages, e.g., passages 220. Similarly,second end 226 includes a number of output openings 230 that communicatecleaned exhaust from a second set of the passages, e.g., passages 222.Hence, the plurality of first passages 220 pass adjacent at least oneparticulate filter and are opened only to first end 224 of housing 212.Likewise, the plurality of second passages 222 pass adjacent at leastone particulate filter and are opened only to second end 226 of housing212.

[0075] It should be recognized that the passages to which openings 228,230 are attached may be switched, i.e., passages 222 may be intake andpassages 220 may be output. Depending on the number of filters 214,intake or output openings are also provided for an innermost passage220A and/or an outermost passage, e.g., passage 220C (FIG. 10).

[0076] In operation, exhaust 52 delivered to first end 224 passesthrough an intake opening 228 of first end 224 of housing 212, through apassage 220, and through a first, intake side of a particulate filter214. As the exhaust moves through particulate filter 214, the filterremoves particulates from exhaust 52. The cleaned exhaust then exits arespective particulate filter 214 at an output side into a secondpassage 222. Thereafter, the cleaned exhaust exits from an outputopening 230 in second end 226 of housing 212. Subsequently, the cleanedexhaust is passed to one or more subsequent dual-pass filters 14 orexits filter system 10, depending on the positioning of filter unit 210,as described above.

[0077] It should be understood that particulate filter unit 210 may becombined, modified and/or applied as described relative to precedingembodiments of the invention. For instance, regeneration system 64 isequally applicable to a filter system having filter unit 210.

[0078] While this invention has been described in conjunction with thespecific embodiments outlined above, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the preferred embodiments of theinvention as set forth above are intended to be illustrative, notlimiting. Various changes may be made without departing from the spiritand scope of the invention as defined in the following claims.

What is claimed is:
 1. A filter unit for an exhaust removing filtersystem having one or more attachable units for varying the size of thefilter system, the filter unit comprising: a housing; a plurality ofconcentrically arranged particulate filters within the housing; aplurality of first passages passing adjacent at least one particulatefilter and opened to a first end of the housing; and a plurality ofsecond passages passing adjacent at least one particulate filter andopened to a second end of the housing; whereby exhaust passes throughone of the particulate filters as the exhaust moves from the firstpassages to the second passages.
 2. The filter unit of claim 1, whereinthe housing includes an outer shell and an inner shell.
 3. The filterunit of claim 2, wherein the inner shell is concentrically positionedwithin an innermost particulate filter.
 4. The filter unit of claim 2,further comprising a third passage extending between one of an outermostparticulate filter and the outer shell, and a fourth passage extendingbetween an innermost particulate filter and the inner shell.
 5. Thefilter unit of claim 4, wherein the housing includes a first end havingopenings communicating with the plurality of first passages and a secondend having openings communicating with the second passages.
 6. Thefilter unit of claim 5, wherein the housing includes an opening at oneof the first and second ends communicating with the third passage, andan opening at one of the first and second ends communicating with thefourth passage.
 7. The filter unit of claim 1, wherein each particulatefilter includes an outer porous shell, a filter section within the outerporous shell, and an inner porous shell within the filter section. 8.The filter unit of claim 1, wherein the housing includes a first endhaving openings communicating with the plurality of first passages and asecond end having openings communicating with the second passages.
 9. Afilter system for removing soot from exhaust of an exhaust producingdevice, the filter system comprising one or more attachable units forvarying the size of the filter system, the system comprising: aparticulate filter unit; and one or more combination particulate andnitrogen oxide filter units.
 10. The filter system of claim 9, whereinthe particulate filter unit includes: a particulate filter unit housing;a plurality of concentrically arranged particulate filters within theparticulate filter unit housing; a plurality of first passages passingadjacent at least one particulate filter and opened to a first end ofthe particulate filter unit housing; a plurality of second passagespassing adjacent at least one particulate filter and opened to a secondend of the particulate filter unit housing; whereby exhaust passesthrough a particulate filter as the exhaust moves from the firstpassages to the second passages.
 11. The filter system of claim 10,wherein the particular filter is made of a material chosen from thegroup comprising: ceramic fiber paper, ceramic cloth and ceramic wovenfiber.
 12. The filter system of claim 11, wherein the material is coatedwith a pre-ceramic polymer chosen from the group comprising: siliconcarbide, oxycarbide, aluminosilicate and alumina.
 13. The filter systemof claim 9, wherein each combination filter unit includes: a housing; aparticulate filter section positioned within the housing; and a nitrogenoxide filter section having a gas-impervious inner cylinder spacedwithin the particulate filter section and a nitrogen-oxide removingcatalyst positioned within the inner cylinder.
 14. The filter system ofclaim 13, wherein, in each combination filter unit, exhaust gases passradially through the particulate filter section and longitudinallythrough the nitrogen oxide filter section.
 15. The filter system ofclaim 13, wherein the gas impervious cylinder has open ends and isspaced from an inner portion of the particulate filter section.
 16. Thefilter system of claim 13, wherein the nitrogen oxide filter section isshorter in length than the particulate filter section.
 17. The filtersystem of claim 13, wherein each combination filter unit furthercomprises: a porous cylinder for supporting an inner portion of theparticulate filter section; and a first end cap for spacing the nitrogenoxide filter section concentrically within the particulate filtersection.
 18. The filter system of claim 13, wherein each combinationfilter unit further comprises a second end cap for spacing the nitrogenoxide filter section concentrically within the particulate filtersection.
 19. The filter system of claim 13, wherein the gas imperviouscylinder includes a vent port for mating with an adjacent unit.
 20. Thefilter system of claim 13, wherein the particulate filter section isspaced from an inner surface of the second stage unit housing.
 21. Thefilter system of claim 13, wherein the particular filter section is madeof a material chosen from the group comprising: ceramic fiber paper,ceramic cloth and ceramic woven fiber.
 22. The filter system of claim21, wherein the particulate filter section includes one of a set ofradially oriented plates of the material and a set of radially orientedpleats of the material.
 23. The filter system of claim 21, wherein thematerial is coated with a pre-ceramic polymer chosen from the groupcomprising: silicon carbide, oxycarbide, aluminosilicate and alumina.24. A filter system for removing soot from exhaust of an exhaustproducing device, the filter system comprising one or more attachableunits for varying the size of the filter system, the system comprising:a first stage unit housing; a plurality of concentrically arrangedparticulate filters within the first stage unit housing; a plurality offirst passages passing adjacent at least one particulate filter andopened to a first end of the first unit stage housing; a plurality ofsecond passages passing adjacent at least one particulate filter andopened to a second end of the first unit stage housing; whereby exhaustpasses through a particulate filter as the exhaust moves from the firstpassages to the second passages; and one or more second stage units,each second stage unit including: a second stage unit housing; aparticulate filter section positioned within the second stage unithousing; and a nitrogen oxide filter section having a gas-imperviousinner cylinder spaced within the particulate filter section and anitrogen-oxide removing catalyst positioned within the inner cylinder.25. The filter system of claim 24, wherein the first and second stagehousings each include: an outer metal shell; and a coupling forsequentially attaching a unit to an adjacent unit.
 26. A filter unit foran exhaust removing filter system having one or more attachable unitsfor varying the size of the filter system, the filter unit comprising: ahousing; a plurality of concentrically arranged particulate filterswithin the housing; a set of intake openings in a first end of thehousing, each intake opening communicating with a passage extendingadjacent an intake side of at least one particulate filter; a set ofoutput openings in a second end of the housing, each output openingcommunicating with a passage extending adjacent an output side of atleast one particulate filter; and wherein exhaust enters the intakeopenings, passes through a respective particulate filter and exitsthrough the output openings.
 27. A filter system for removing soot fromexhaust of an exhaust producing device, the filter system comprising oneor more attachable units for varying the size of the filter system, eachunit including: means for housing filter components; means for filteringparticulates positioned within the means for housing; and means forfiltering particulates and nitrogen oxide.
 28. The filter system ofclaim 27, further comprising means for regenerating the filter system.29. A filter system for removing soot from exhaust of an exhaustproducing device, the filter system comprising one or more attachableunits for varying the size of the filter system, the system comprising:a particulate filter unit including a particulate filter unit housing; aplurality of concentrically arranged particulate filters within theparticulate filter unit housing; a plurality of first passages passingadjacent at least one particulate filter and opened to a first end ofthe first unit stage housing; a plurality of second passages passingadjacent at least one particulate filter and opened to a second end ofthe first unit stage housing; whereby exhaust passes through aparticulate filter as the exhaust moves from the first passages to thesecond passages; and one or more combination filter units eachincluding: a combination filter unit housing having an outer shell and acoupling adapted to attach a unit to an adjacent unit; a particulatefilter section positioned within the combination filter unit housing; aporous cylinder for supporting an inner portion of the particulatefilter section; a gas-impervious inner cylinder spaced within the porouscylinder; and a nitrogen-oxide removing catalyst positioned within theinner cylinder, wherein exhaust gases pass radially through theparticulate filter section and longitudinally through the nitrogen oxidefilter.
 30. The filter system of claim 29, wherein the plurality ofparticulate filters of the particulate filter unit and the particulatefilter section of each combination filter unit are coated with apre-ceramic polymer chosen from the group comprising: silicon carbide,oxycarbide, aluminosilicate and alumina.